Fine powder of high molecular weight fluorine containing fused resins, its mold goods, and the dedicated production methods

ABSTRACT

The fine powder of high molecular weight fluorine containing resins having melt viscosities of 10 6  to 10 13  poise, apparent density of 0.4 to 1.5 g/cc, and specific surface area of 2 m 2 /g or less, mold goods of the fine powder and these production methods. By utilizing the fine powder of high molecular weight flourine containing fused resins that have previously not been employed, the mold goods obtained from the fine powder have fewer liquated particles and have become the most suitable especially for manufacturing semiconductors. The powder&#39;s products have greater resistance to flex fatigue, abrasion, resistance, etc.

FIELD OF THE INVENTION

This invention relates to (a) the fine powder of high molecular weightfluorine containing fused resins (this fine powder is especiallysuitable in producing jigs, etc. used in the manufacturing processes ofsemiconductors), (b) mold goods obtained by molding this fine powder,and (c) these production methods.

BACKGROUND OF THE INVENTION

Inasmuch as fluorine containing fused resins are especially excellent inheat resistance, chemical resistance, electrical insulation, nonviscousproperty, lower friction property, etc. among many kinds of plastics,they are applied in fields ranging from the space development andaircraft industries to the household goods industry, chemical industry,the electric and electronic industries, and the machine industry.

It is comparatively difficult, however, to mold fluorine containingfused resins because they have higher melt viscosities and narrowerranges of proper mold processing conditions as compared with othergeneral-purpose plastics. Such resins, moreover, may decompose slightlyat high molding temperatures to produce corrosive gases. Especially, ashigh molecular weight resins having a melt viscosity of 10⁶ or greaterpoise are excessively high in melt viscosity and very low in fluidity,it is very difficult to mold them by ordinary extrusion molding andinjection molding. As a result, these resins have so far been without anapplication.

Conversely, as appreciated from the case of superhigh molecular weightpolyethylene, plastics generally develop merits with increased molecularweight. It is thus possible to improve mechanical properties, includingstrength, modulus of elasticity, abrasion resistance and resistance toflex fatigue; and to improve chemical properties such as weatherabilityand chemical resistance. It is therefore naturally expected thatvaluable improvements of properties can be achieved also in fluorinecontaining fused resins by increasing their molecular weight. Suchimprovements, however, have not been utilized practically because of theabove-mentioned molding difficulty. Rather, techniques of lowering themolecular weight of fluorine containing resins have been studied whilemaintaining their mechanical and chemical properties.

Furthermore, although fluorine containing fused resins are usuallymolded by extrusion and injection, the resins are supplied in the formof pellets, as with other general-purpose plastics. This is done tosecure a good supply of raw materials for molding machines, includingfacile dropping through hoppers and feeding into the screws, and to makethe handling of raw materials easy.

High molecular weight resins, however, having melt viscosities of 10⁶ orgreater poise are difficult to pelletize because of excessive meltviscosity.

Accordingly, there exists no alternative to their being supplied in theform of powder as they are. Powder, however, immediately followingpolymerization has low apparent density and inferior fluidity, makingits supply unstable. This has also been a factor obstructing thepractical use of high molecular weight fluorine containing fused resins.

Conversely, inasmuch as fluorine containing fused resins have theabove-mentioned excellent properties, it is the ingredient of choice inthe manufacturing processes of semiconductors as mold goods such aswafer carriers, tubes, joints, square brackets, etc. Because LSI ishighly integrated and concentrated, minute amounts of impurities such asparticles, metals, etc. have come into question. Concerning mold goodsof fluorine containing fused resins used in these applications, thedemand for high purity is also increasing.

Accordingly, the liquation of particles from mold goods of fluorinecontaining fused resins is a problem. Proposed to decrease the number ofliquated particles have been a method for extracting these particleswith a fluorine-containing solvent, and a method of washing mold goodswith isopropyl alcohol, etc. Both methods, however, have problems incost and productivity because they are after-treatments conducted bymeans of special equipment and chemical liquids.

SUMMARY OF THE INVENTION

The purposes of this invention are (a) to improve the properties of finepowder of high molecular weight fluorine containing fused resins thathave not been utilized, (b) to offer mold goods that have diminishednumbers of liquated particles and that are preferable to themanufacturing processes of semiconductors by molding the fine powder,and (c) to offer the production methods of these mold goods.

DETAILED DESCRIPTION OF THE INVENTION

This invention thus relates (a) to the fine powder of high molecularweight fluorine containing fused resins having melt viscosities of 10⁶to 10¹⁰ poise, apparent densities of 0.4 to 1.5 g/cc, and specificsurface areas of 2 m²/g or less; and (b) to mold goods obtained bymolding the fine powder.

As the kinds of fluorine containing fused resins in this invention, atleast one kind of resins are given that are selected from the resingroup composed of copolymers of tetrafluoro ethylene and perfluoroalkylvinyl ether (hereinafter “PFA”), copolymers of tetrafluoroethyleneand hexafluoropropene (hereinafter “FEP”), copolymers of tetrafluoroethylene and ethylene (hereinafter “ETFE”), vinylidene fluoridehomopolymers (hereinafter “PVDF”), copolymers of vinylidene fluoride andtetrafluoro ethylene, copolymers of vinylidene fluoride andhexafluoropropene, copolymers of vinylidene fluoride andchlorotrifluoroethylene, copolymers of chlorotrifluoroethylene andethylene (hereinafter “ECTFE”), etc. Here, a copolymer PFA is preferableto be a copolymer of tetrafluoro ethylene and at least one kind ofperfluoro alkylvinyl ethers as expressed by the formula CF₂═CFO(CF₂)mF(in this formula, m is an integral number of one to six), or a formulaCF₂═CF(O—CF₂CF(CF₃))nOC₃F₇ (in this formula, n is an integral number of1 to 4); and is especially preferable to be a copolymer of tetrafluoroethylene of 92% to 99% and perfluoro alkylvinyl ether of 1% to 8% byweight. Further, FEP is preferable to be a copolymer of tetrafluoroethylene of 72% to 96% and hexafluoropropene of 4% to 28% by weight.ETFE is preferable to be a copolymer of tetrafluoro ethylene of 74.5% to89.3% and ethylene of 10.7% to 25.5% by weight. These fluororesins areallowed to be copolymerized with other monomers in an amount notadversely to affect the essential properties of each resin. As the othermonomers, the following compounds are given as examples: (a) tetrafluoroethylene, (b) chlorotrifluoroethylene, (c) hexafluoropropene, (c)perfluoro alkylvinyl ether, (d) fluoroalkyl (C1 to C10) ethylene, (e)perfluoroalkyl (C1 to C10) allyl ether, (f) compounds expressed by theformula CF₂═CF[OCF₂CFRf(CF₂)p]qOCF₂(CF₂)rY (in this formula, Rf isfluorine atom or trifluoro methyl radical, Y is a halogen atom, p is 0or 1, q is 0 or an integral number of 1 to 5, r is 0 or an integralnumber of 1 to 2. When, however, p is 1, Rf is fluorine atom), and (g)compounds expressed by the formula CH₂=CF(CF₂)nX (in this formula, n isan integral number of 0 to 8, and X is a hydrogen or fluorine atom).

The melt viscosity of fluorine containing fused resins in this inventionmust indispensably be 10⁶ to 10¹⁰ poise from the point of view ofdecreasing the number of liquated particles and improving the quality ofmold goods,. Those resins having melt viscosity of less than 10⁶ poise,which are collectively called fluorine containing fused resins and areusually commercially available for mold processing, are not preferablebecause they have lower mechanical properties and large numbers ofliquated particles as will be mentioned later. Furthermore, in case ofresins having melt viscosities of more than 10¹⁰ poise, their moldprocessing temperatures cannot help being increased over the startingtemperatures of their thermal decompositions to obtain favorable moldgoods. Accordingly, these resins are not preferable because their moldgoods are foamed and colored.

Generally, resins of high molecular weights that have not hitherto beenused—those having melt viscosities of more than 10⁶ poise—are objects ofthis invention. The polymerization methods, however, of fluorinecontaining fused resins to be used in this invention are unlimited.Generally well-known methods, such as emulsion polymerization,suspension polymerization, solution polymerization, and bulkpolymerization, can be used in producing the resins.

The apparent density of the fine powder of fluorine containing fusedresins in this invention must indispensably be 0.4 to 1.5 g/cc from thepoint of view of powder fluidity, moldability,and improving the qualityof mold goods, and is preferably 0.5 to 1.4 g/cc. Those resins havingapparent density of less than 0.4 g/cc show bad powder fluidity and areapt unevenly to be filled in dies in case of injection molding andcompression molding, resulting in failure to produce favorable moldgoods. Further, those resins having apparent densities exceeding 1.5g/cc also do not produce favorable mold goods because the powderparticles cannot sufficiently be mutually welded.

The specific surface area of the fine powder of fluorine containingfused resins in this invention must indispensably be 2 m²/g or less fromthe point of view of powder fluidity, and preferably should be 1 m²/g orless. If the specific surface area is greater than 2 m²/g, powderfluidity is low as a result of insufficient firmness of the powderparticles. Such powder is not preferable especially for molding withscrews, such as in injection molding, because the powder isinsufficiently taken into the screws. The average particle size rangesfrom 10 to 2,000 μm and preferably would be from 50 to 1,000 μm

The raw material powder of fluorine containing fused resins (raw powder)just after polymerization (after coagulation in case of emulsionpolymerization) has insufficient firmness with an apparent density ofless than 0.4 g/cc and a specific surface area exceeding 2 m²/g.Accordingly, for the above-mentioned reason, this raw powder cannot besupplied to molding machines because it requires increased apparentdensity and decreased specific surface area.

As methods in this treatment, the following examples are shown. Rawpowder of high molecular weight fluorine containing fused resins isheated at temperatures between (m.p.−10° C. ) and (m.p.+20° C.),preferably at temperatures between m.p.+10° C. , to be welded partially.Then the raw powder is ground. On this occasion if raw powder is heatedat temperatures exceeding m.p.20° C., it will be welded excessively andbecome difficult to grind, resulting in decreased apparent density.Further, if raw powder is heated at temperatures below(m.p.−10° C.), itwill be welded insufficiently, resulting in failed diminished specificsurface area as a result of inadequate firmness.

Furthermore, it is possible to adopt a method whereby raw powder of highmolecular weight fluorine containing fused resins is rolled attemperatures below (m.p.−10° C.), and under pressures of preferably 2kg/cm² or more, to make compressed plate-like products, which arefinally ground. Although no restriction will be imposed on the method ofgrinding, and ordinary grinders can be used, it is preferable to use aHenschel grinder, rotor speed mill, etc.

According to these methods, it is possible to obtain a fine powder ofhigh molecular weight fluorine containing fused resins with apparentdensities of 0.4 to 1.5 g/cc and specific surface areas of 2 m²/g orless. This fine powder has good powder fluidity and will ensure a goodsupply of raw materials to molding machines. Accordingly, the followingkinds of molding will become possible.

Only a small change is needed for conventional molding methods to usethem as molding methods in this invention, despite the fact that thefluorine containing fused resins to be used have the above-mentionedproperties.

The applicable molding methods include compression molding, isostaticmolding, transfer molding, ram extrusion molding, extrusion molding,injection molding, blow molding, and flashflow molding.

Molding conditions vary depending on each molding method. Inasmuch,however, as resins of this invention are high in molecular weight andmelt viscosity, it is preferable to raise the molding temperatures anddie temperatures by 10° to 60° C. , and to raise the molding pressuresby 50 to 100 kg/cm² while injection time and pouring time aredecelerated by 10 to 100 sec. and the cooling time lengthened by 50 to100 sec., compared with the molding conditions for conventional fluorinecontaining fused resins. Molding temperatures must be kept below thethermal decomposition starting temperatures of the resins to be used toprevent mold goods from being foamed and colored.

According to these molding methods, mold goods having desired shapes canbe obtained. These include mold goods of complicated shapes such aswafer carriers, wafer boxes, bolts, beakers, filter housings,flowmeters, pumps, valves, cocks, connecting joints, connectors, andnuts; as well as simple mold goods such as sheets, films, gasket,rods,square rods, pipes, tubes, electric wires, circular brackets,square brackets, and tanks.

The mold goods based on this invention are those obtained by using highmolecular weight resins that have thus far not been utilized.Accordingly, the rate of lower molecular weight materials in resins hasdiminished relatively.

Meanwhile, as the main cause of the occurrence of liquated particlesfrom mold goods, which has come into question in the manufacturingprocesses of semiconductors, it is pointed out that lower molecularweight materials in the resins dissolve in chemical liquids.Accordingly, mold goods based on this invention are best suited for themanufacturing processes of semiconductors because they have a smallnumber of liquated particles.

The fine powder of high molecular weight fluorine containing resinsbased on this invention is the fine powder of high molecular weightfluorine containing fused resins having a melt viscosity of 10⁶ to 10¹³poise, apparent density of 0.4 to 1.5 g/cc, and specific surface area of2 m²/g or less, such as not previously been used. Accordingly, moldgoods obtained by employing this fine powder have fewer liquatedparticles and are particularly suited for the manufacturing processes ofsemiconductors. Furthermore, it will be also possible to improve theproperties of the mold goods, such as flex fatigue resistance andabrasion resistance.

EXAMPLE

This invention will be explained in detail in the following exampleswith reference to Comparative Examples. This invention, however, shouldnot be restricted solely to these examples.

The word “part” in the following examples means the weight factor unlessotherwise indicated.

First, the measurement of each physical property in the followingexamples was made according to the following plans.

(1) Melt Viscosity

Melt viscosity was measured using a capillary flow tester (ShimazuCorp.). Two grams of the resin to be measured were infused into acylinder 9.5 mm in inside diameter and heated for 5 min. for maintenanceat the following temperature. Then the resin was extruded under 7 kg/cm²of piston load through an orifice 2.1 mm in inside diameter and 8 mm inlength. Melt viscosity was calculated in poise from the extrusion speedof this test.

PFA and FEP: 380° C.

ETFE and ECTFE: 300° C.

PVDF: 230° C.

(2) Melting Point

This is a value (° C.) that was measured by a differential scanningcalorimeter (DSC-7, Perkin Elmer Co.) at a temperature-raising speed of10° C./min.

(3) Starting Temperature of Thermal Decomposition

This is a value (° C.) that was measured by a thermal gravimetricanalyzer (TGA-50, Shimazu Seisakusho Co.) at a temperature-raising speedof 10° C./min.

(4) Apparent Density

Measurement followed JIS K-6891. After powder samples were droppedthrough a damper into a cylindrical stainless vessel 30 cc in insidevolume, surplus powder was rubbed off by a flat plate. The apparentdensity is a value (g/cc) obtained by dividing the weight of theremaining sample (g) by the inside volume (cc).

(5) Specific Surface Area

This is a value (m²/g) that was measured by a direct reading typespecific surface area apparatus (Monosorb, Yuasa Aionix Co.).

(6) MIT Value (Resistance to Flex Fatigue)

Measurement followed ASTM D-2176. A MIT type flex fatigue resistancetester (Toyo Seiki Seisakusho Co.) was used. Test pieces were out offfrom compression molding sheets 0.20 to 0.23 mm in thickness. The testpieces were measured under the condition of a load of 1.25 kgf, a flexspeed of 178 times/min., and a flex angle of 135° .

(7) Taber Abrasion Index (Abrasion Resistance)

Measurement followed JIS K-7204. Compression molding sheets 1 mm inthickness and 102 mm in diameter were used as test pieces and measuredby a Taber abrasion testing machine (No. 410, Toyo Seiki SeisakushoCo.).

Abrasion tests were conducted under the condition of using CS-10 as anabrasion wheel, applying a load of 1 kgf, and abrading 2,000 times at 70rpm. The Taber abrasion index is indicated as the figure of abrasionloss (mg) per 1,000 times abrasion.

Comparative Example 1

(Commercially Available PFA Used)

Using commercially available PFA pellets having a melt viscosity of3.1×10⁴ poise (Neoflon PFA AP-210, Daikin Kogyo Co., Ltd.) as a rawmaterial, injection molding was conducted using an injection moldingmachine with a disk mold (100 mm¢, 2 mm in thickness) under the moldingconditions shown in the following Table 1. In such molding, raw materialPFA was fed into a cylinder with a nozzle through a hopper and melted byraising the temperature of the cylinder.

Then, being injected into the cavity through the nozzle, the meltedfluoro resin was compressed by a compression plate under a compressionpressure of 30 kgf/cm².

The raw material used in this molding was smoothly supplied, fromdropping through the hopper to being taken into the screws, and stablymeasured, resulting in normal molding. The obtained mold goods had goodquality, having no foamed or colored part, as well as no whitened partfrom insufficient welding or melting.

Comparative Example 2

(Commercially Available PFA Used)

Using commercially available PFA pellets having melt viscosity of2.5×10⁵ poise (Neoflon PFA AP-230, Daikin Kogyo Co., Ltd.) as a rawmaterial, injection molding was conducted using the same injectionmolding machine as in Comparative Example 1 under the molding conditionsshown in the following Table 1.

This material was smoothly supplied, from dropping through the hopper tobeing taken into the screws, and stably measured, resulting in normalmolding. The obtained mold goods had good quality, having no foamed orcolored part, as well as no whitened part as a result of insufficientwelding or melting.

Comparative Example 3

(High Molecular Weight PFA Used)

In a glass-lined autoclave with a jacket equipped with a stirrer with acapacity of 4,000 parts water, 1,040 parts of decarbonated anddemineralized water were fed. After being sufficiently substituted withpure nitrogen gas, the inner space was vacuumed. Then 800 parts of1,2-dichloro-1,1,2,2-tetrafluoro ethane (hereinafter “R-114”) and 40parts of perfluoropropyl vinyl ether(hereinafter “PPVE”) were fed.

Stirring the mixture and keeping the internal temperature at 15° C. ,tetrafluoroethylene (hereinafter “TFE”) was fed under pressure to keepthe internal pressure of the autoclave at 2.4 kg/cm² G.

When three parts ofbis-(2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptanoyl)-peroxide(hereinafter “DHP”) were added to the mixture as a polymerizationinitiator, the reaction started immediately. As pressure drops with theprogress of the reaction, TFE was additionally fed under pressure tokeep the internal pressure in the autoclave at 2.4 kg/cm² G. After thereaction was conducted for 130 min., stirring was stopped. Then theunreacted monomer and R-114 were purged.

The white powder produced within the autoclave was washed and dried at120° C. for 12 hours. Thus 270 parts of the intended high molecularweight PFA powder was obtained. Concerning the physical properties ofthis PFA, it was confirmed that the melt viscosity was 4.2×10⁶ poise andthe PPVE content was 3.2 wt % (measured by melting NMR measurement).Other physical properties were as shown in the following Table 1.

Using this high molecular weight PFA as the raw material, injectionmolding was tried by using the same injection molding machine as inComparative Example 1 under the molding conditions shown in thefollowing Table 1. The raw material, however, only turned round on thescrew parts and was difficult to charge. Although the raw material waspoked by a rod from the hopper part to be charged, its weighing wasunstable. Accordingly, no favorable mold goods could be obtained.

Example 1

(High Molecular Weight PFA Used)

After the high molecular weight PFA powder that had been obtained inComparative Example 3 was heated at 310° C. for six hours in an electricfurnace, the powder was ground by a Henschel grinding machine for 10min. The physical properties of the obtained fine powder of highmolecular weight PFA were as shown in the following Table 1.

Using this high molecular weight PFA as the raw material, injectionmolding was tried under the same molding conditions as in ComparativeExample 3. This material was smoothly supplied, from dropping throughthe hopper to being taken into the screws, and stably measured,resulting in normal molding. The obtained mold goods had good quality,having no foamed or colored part, as well as no whitened part as aresult of insufficient welding or melting. Moreover, the flex fatigueresistance and abrasion resistance were greatly improved.

Comparative Example 4

(Commercially Available FEP Used)

Using commercially available FEP pellets having melt viscosity of7.5×10⁴ poise (Neoflon FEP NP-20, Daikin Kogyo Co., Ltd.) as a rawmaterial, compression molding was conducted with a compression moldingmold under the molding conditions shown in the following Table 2. Themold is designed to compress resins between the two molds: an upper moldand a lower one.

The obtained sheet-like mold goods had good quality, having no foamed orcolored part, as well as no whitened part resulting from insufficientwelding or melting.

Comparative Example 5

(Commercially Available FEP Used)

Using commercially available FEP pellets having melt viscosity of4.0×10⁵ poise (Neoflon FEP NP-40, Daikin Kogyo Co., Ltd.) as a rawmaterial, compression molding was conducted with the same compressionmolding die used in Comparative Example 4, under the molding conditionsshown in the following Table 2.

The obtained sheet-like mold goods had good quality, having no foamed orcolored part, as well as no whitened part resulting from insufficientwelding or melting.

Comparative Example 6

(High Molecular Weight FEP Used)

In a glass-lined autoclave with a jacket equipped with a stirrer, with acapacity of 4,000 parts water, 1,300 parts of decarbonated anddemineralized water were infused. After being sufficiently substitutedwith pure nitrogen gas, the inner space was vacuumed. Then 1,300 partsof hexafluoropropene (hereinafter “HFP”) were fed. Stirring the mixtureand keeping the internal temperature at 25.5° C. , tetrafluoro ethylene(TFE) was fed under pressure to keep the internal pressure of theautoclave at 9.0 kg/cm² G.

When 1.9 parts of DHP were added to the mixture as a polymerizationinitiator, reaction started immediately. As pressure fell with theprogress of the reaction, TFE was additionally fed under pressure tokeep the internal pressure in the autoclave at 9.0 kg/cm² G. After thereaction was conducted for 240 min., stirring was stopped. Then theunreacted monomer was purged.

The white powder produced within the autoclave was washed and dried at120° C. for 12 hours. Thus 415 parts of the intended superhigh molecularweight FEP powder was obtained. Regarding the physical properties ofthis FEP, it was confirmed that the melt viscosity was 2.9×10⁶ poise andthe HFP content was 8.2 wt % (measured by melting NMR measurement).Other physical properties were as shown in the following Table 2.

Using this high molecular weight FEP as a raw material, compressionmolding was conducted using the same compression molding mold as inComparative Example 4 under the molding conditions shown in thefollowing Table 2.

The obtained sheet-like mold goods were found to have some whitenedparts because of insufficient welding and were thus impracticalproducts.

Example 2

(High Molecular Weight FEP Used)

The high molecular weight FEP powder obtained in Comparative Example 6was hardened to become board-like by using a roller compactor (GBS type,Shinto Kogyo Co.) under the conditions of room temperature and a rollrevolution of 0.4 rpm. The board-like products were then ground at 360rpm by a pulverizer. The obtained fine powder of high molecular weightFEP had the physical properties shown in the following Table 2.

Using this high molecular weight FEP as a raw material, compressionmolding was conducted with the same compression molding mold as used inComparative Example 4 under the molding conditions shown in thefollowing Table 2.

The obtained sheet-like mold goods had good quality, having no foamed orcolored part, as well as no whitened part resulting from insufficientwelding or melting.

Comparative Example 7

(Commercially Available ETFE Used)

Using commercially available ETFE pellets having melt viscosity of2.2×10⁴ poise (Neoflon ETFE EP-521, Daikin Kogyo Co., Ltd.) as a rawmaterial, transfer molding of the resin was conducted with a pot andmold for transfer molding under the molding conditions shown in thefollowing Table 3. The obtained sheet-like mold goods had good quality,having no foamed or colored part, as well as no whitened part because ofinsufficient welding or melting.

Comparative Example 8

(Commercially Available ETFE Used)

Using commercially available ETFE pellets having melt viscosity of4.6×10⁴ poise (Neoflon ETFE EP-541, Daikin Kogyo Co., Ltd.) as a rawmaterial, transfer molding was conducted with a pot and mold fortransfer molding under the molding conditions shown in the followingTable 3. The obtained sheet-like mold goods had good quality, having nofoamed or colored part, as well as no whitened part resulting frominsufficient welding or melting.

Comparative Example 9

(High Molecular Weight ETFE Used)

In a glass-lined autoclave with a jacket equipped with a stirrer, with acapacity of 4,000 parts water, 1,000 parts of decarbonated anddemineralized water were infused. After being sufficiently substitutedwith pure nitrogen gas, the inner space was vacuumed. Then 1,000 partsof R-114 and 5.5 parts of 2,3,3,4,4,5,5-heptafluoro-1-pentene(hereinafter “7FP”) were fed.

Stirring the mixture and keeping the internal temperature at 35° C., TFEand ethylene were fed under pressure to keep the internal pressure ofthe autoclave at 7.5 kg/cm² G and the gas phase composition ofTFE/ethylene at 74/26 (mole ratio).

When two parts of diisopropylperoxy dicarbonate were added to themixture as a polymerization initiator, the reaction started immediately.As the pressure fell with the progress of the reaction, TFE and ethylenewere additionally fed under pressure to keep the internal pressure ofthe autoclave at 7.5 kg/cm² G, and the gas phase composition ofTFE/ethylene at 74/26 (mole ratio). 4.5 parts of 7FP were also added asoccasion demanded. After the reaction was conducted for 150 min.,stirring was stopped. Then the unreacted monomer and R-114 were purged.

White powder produced within the autoclave was washed and dried at 120°C. for 12 hours. Thus 109 parts of the intended high molecular weightETFE powder was obtained. Regarding the physical properties of thisETFE, it was confirmed that the melt viscosity was 6.0×10⁶ poise and thecomposition of the TFE/ethylene/7FP was 76/20/4 (wt %) (measured bymelting NMR measurement). The other physical properties were as shown inthe following Table 3.

Using this high molecular weight ETFE as a raw material, transfermolding was conducted with the same pot and die for transfer molding asused in Comparative Example 7 under the molding conditions shown in thefollowing Table 3.

The obtained sheet-like mold goods were impractical products, beingfound to have whitened parts resulting from insufficient welding andmelting, and to have rough surfaces.

Example 3

(High Molecular Weight ETFE Used)

After the high molecular weight ETFE powder that had been obtained inComparative Example 9 was heated at 255° C. for four hours in anelectric furnace, the powder was ground by a Henschel grinding machinefor 10 min. The physical properties of the obtained fine powder of highmolecular weight ETFE were as shown in the following Table 3.

Using this high molecular weight ETFE as a raw material, transfermolding was conducted under the same molding conditions as inComparative Example 9.

The obtained sheet-like mold goods were of good quality, having nofoamed or colored portion, as well as no whitened part as a result ofinsufficient welding or melting. Abrasion resistance was also improved.

Example 4

(Measurement of Liquated Particles)

From each of the mold goods obtained in Comparative Examples 1, 2, 4, 5,7, and 8, and from Examples 1, 2, and 3, five dumbbells were stampedout. Particle liquation tests were conducted using these dumbbells. TheType 5 dumbbells described in ASTM D638 were used.

Inasmuch as considerable particles are attached to the surfaces of thesedumbbells as a result of contamination from the atmosphere in theprocesses of molding and stamping, preliminary washing was doneaccording to the following steps to get rid of these particles.

Thus, after being rinsed with ultra-pure water for 5 min., the dumbbellswere put into a clear polyethylene 1-liter bottle. Then fed into thebottle were 200 g of 50% fluoric acid aqueous solution of highly puresemiconductor-grade. The bottle was agitated for 5 min. in a shaker.

The bottle was left for 24 hours before the fluoric acid aqueoussolution was removed. The dumbbells were rinsed again with ultra-purewater for 5 min.

In succession, the dumbbells were soaked in 100 ml of a 4:1 mixture ofsulfuric acid and aqueous hydrogen peroxide—the highly puresemiconductor-grade—for 5 min. and then rinsed again with ultra-purewater for 5 min.

Each of the five preliminarily washed dumbbells were placed in a clearpolyethylene 1-liter bottle. Infused into the bottle were 200 g of 50%fluoric acid aqueous solution—highly pure semiconductor-grade. This wasagitated for 5 min. in a shaker.

After being left for 24 hours, the particles (0.2 μm or more) in fluoricacid aqueous solution were counted by a particle counter (KL-22, RionCo.).

The counting results of liquated particles are shown in the followingTable 4. The value counted by the same method except for the dumbbellsis also shown in Table 4 as reference. Only dumbbells made of highmolecular weight fluorine containing resins as in Examples 1 to 3 showedminimal numbers of liquated particles.

TABLE 1 (Physical Properties of PFA and Examples of its Mold Goods)Comparative Comparative Example 1 Example 2 Comparative CommerciallyCommercially Example 3 Example 1 available available High molecular Highmolecular Items Units low viscosity high viscosity weight weightPhysical properties of raw materials Melt viscosity poise 3.1 × 10⁴ 2.5× 10⁵ 4.2 × 10⁶ 4.2 × 10⁶ melting point ° C. 309 309 309 309 Startingtemperature of ° C. 417 430 443 443 thermal Decomposition apparentdensity g/cc 1.21 1.21 0.38 0.78 Specific surface area m²/g — — 4.570.24 Average particle diameter μm — — — 180 MIT value cycle 17,000812,000 — 10,050,000 Taber abrasion index mg 7.7 5.8 — 4.4 Moldingconditions Molding temperature ° C. 370 420 430 430 Temperature of themold ° C. 180 200 230 230 Injection pressure kg/cm² 30 30 30 30Injection time sec. 25 60 100 100 Cooling time sec. 80 90 150 150Appearance of mold Good Good Some whitened Good goods parts and roughsurface

TABLE 2 (Physical Properties of FEP and Examples of its Mold Goods)Comparative Comparative Example 4 Example 5 Comparative CommerciallyCommercially Example 6 Example 2 available available High molecular Highmolecular Items Units low viscosity high viscosity weight weightPhysical properties of raw materials Melt viscosity poise 7.5 × 10⁴ 4.0× 10⁵ 2.9 × 10⁶ 2.9 × 10⁶ melting point ° C. 269 268 275 275 Startingtemperature of ° C. 413 415 425 425 thermal Decomposition apparentdensity g/cc 1.21 1.14 0.34 0.63 Specific surface area m²/g — — 7.211.02 Molding conditions Molding temperature ° C. 350 350 380 380 Moldingpressure kg/cm² 50 50 100 100 Pressuring time min. 30 30 40 40 Coolingpressure kg/cm² 50 50 100 100 Cooling time min. 5 5 5 5 Appearance ofmold Good Good Some whitened Good goods parts

TABLE 3 (Physical Properties of ETFE and Examples of its Mold Goods)Comparative Comparative Example 7 Example 8 Comparative CommerciallyCommercially Example 9 Example 3 available available High molecular Highmolecular Items Units low viscosity high viscosity weight weightPhysical properties of raw materials Melt viscosity poise 2.2 × 10⁴ 4.6× 10⁴ 6.0 × 10⁶ 6.0 × 10⁶ melting point ° C. 266 265 265 265 Startingtemperature of ° C. 345 346 346 346 thermal Decomposition apparentdensity g/cc 1.01 1.00 0.25 0.42 Specific surface area m²/g — — 8.071.67 Average particle diameter μm — — — 178 Taber abrasion index mg 10.810.0 — 8.5 Molding conditions Pot temperature ° C. 290 300 330 330 Moldtemperature ° C. 250 260 270 270 Pouring time sec. 30 50 60 60 Moldingpressure kg/cm² 100 150 200 200 Cooling time ° C. 50 50 50 50 Appearanceof mold Good Good Some whitened Good goods parts and rough surface

TABLE 4 (Number of Liquated Particles (unit: Particles/ml)) Referenceexample  10 Comparative Example 1 476 Comparative Example 2 703 Example1 241 Comparative Example 4 638 Comparative Example 5 623 Example 2 307Comparative Example 7 862 Comparative Example 8 912 Example 3 409

As clearly demonstrated by the above results, mold goods produced fromthe fine powder of high molecular weight fluorine containing resinsbased on this invention are excellent in flex fatigue resistance andabrasion resistance. Such goods have the advantage of reducing thenumber of liquated particles by half as compared with conventional moldgoods. Accordingly, the mold goods based on this invention are bestsuited for semiconductor manufacturing applications.

What is claimed is:
 1. A fine powder of high molecular weight fluorinecontaining melt-processible fused resins having melt viscosities of2.9×10⁶ to 6.0×10⁶ poise, apparent densities of 0.4 to 1.5 g/cc, andspecific surface areas of 2 m²/g maximum, said high molecular weightfluorine containing melt-processible fused resins comprising at leastone kind of fluorine containing resin selected from the group consistingof copolymers of tetrafluoroethylene and perfluoro alkylvinyl ether,copolymers of tetrafluoroethylene and hexafluoropropene, copolymers oftetrafluoroethylene and ethylene, vinylidene fluoride homopolymer,copolymers of vinylidene fluoride and tetrafluoroethylene, copolymers ofvinylidene fluorine and hexafluoropropene, copolymers of vinyleidenefluoride and chlorotrifluoreothylene, and copolymers ofchlorotrifluoroethylene and ethylene, wherein the tetrafluoroethylenecopolymers consist of tetrafluoroethylene as a predominant constituentof not less than 72% by weight to not more than 99% by weight, and othercopolymerizable monomer.
 2. Mold goods obtained by molding the finepowder of high molecular weight fluorine containing fused resins asdefined in claim
 1. 3. Mold goods as defined in claim 2, wherein thegoods are jigs used in manufacturing processes of semiconductors.
 4. Amethod of producing fine powder of high molecular weight fluorinecontaining melt-processible fused resins comprising the steps of heatingraw material powder of fluorine containing melt-processible fused resinsjust after polymerization, as defined in claim 1, at temperaturesbetween 10° C. below a melting point of the fluorine containingmelt-processible fused resins and 20° C. above the melting point of thefluorine containing melt-processible fused resins, and then grinding theheated powder.
 5. A method of producing fine powder of high molecularweight fluorine containing melt-processible fused resins comprising thesteps of rolling raw material powder of fluorine containingmelt-processible fused resins just after polymerization, as defined inclaim 1 at temperatures at least 10° C. below a melting point of thefluorine containing melt processible fused resins to make a board-likeproduct, which is then ground.
 6. Mold goods as defined in claim 2,wherein the goods are wafer carriers, tubes, joints and square bracketsused in manufacturing processes of semiconductors.